hw/i386/kvmvapic: Inline sysbus_address_space()

sysbus_address_space(...) is a simple wrapper to
get_system_memory(). Use it in place, since KVM
VAPIC doesn't distinct address spaces.

Rename the 'as' variable as 'mr' since it is a
MemoryRegion type, not an AddressSpace one.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240216153517.49422-6-philmd@linaro.org>

hw/i386/kvmvapic.c

@@ -58,6 +58,7 @@ typedef struct GuestROMState {
 
 struct VAPICROMState {
     SysBusDevice busdev;
+
     MemoryRegion io;
     MemoryRegion rom;
     uint32_t state;
@@ -581,19 +582,17 @@ static int vapic_map_rom_writable(VAPICROMState *s)
 {
     hwaddr rom_paddr = s->rom_state_paddr & ROM_BLOCK_MASK;
     MemoryRegionSection section;
-    MemoryRegion *as;
+    MemoryRegion *mr = get_system_memory();
     size_t rom_size;
     uint8_t *ram;
 
-    as = sysbus_address_space(&s->busdev);
-
     if (s->rom_mapped_writable) {
-        memory_region_del_subregion(as, &s->rom);
+        memory_region_del_subregion(mr, &s->rom);
         object_unparent(OBJECT(&s->rom));
     }
 
     /* grab RAM memory region (region @rom_paddr may still be pc.rom) */
-    section = memory_region_find(as, 0, 1);
+    section = memory_region_find(mr, 0, 1);
 
     /* read ROM size from RAM region */
     if (rom_paddr + 2 >= memory_region_size(section.mr)) {
@@ -614,7 +613,7 @@ static int vapic_map_rom_writable(VAPICROMState *s)
 
     memory_region_init_alias(&s->rom, OBJECT(s), "kvmvapic-rom", section.mr,
                              rom_paddr, rom_size);
-    memory_region_add_subregion_overlap(as, rom_paddr, &s->rom, 1000);
+    memory_region_add_subregion_overlap(mr, rom_paddr, &s->rom, 1000);
     s->rom_mapped_writable = true;
     memory_region_unref(section.mr);